Technically speaking, poltergeists are not yuurei, but there are no other appropriate classifications for them so they are described here.

The Prismriver Ensemble is a so-called phantom ensemble(*1) that are often called to perform at events such as youkai parties.

They're famous for playing vigorous songs with a strong rhythm, so they are the most well-known band in Gensokyo.

The ensemble is composed of three poltergeist sisters; Lunasa is the oldest of the three and excels at the violin.

She appears to be the leader of the Prismriver Ensemble.

Her height is around that of a teenaged human girl.

Her appearance does not differ significantly from a human's.

Her violin is said to be the yuurei of an instrument that would outclass even a Stradivarius(*2), but it's unknown whether this is true or not.

In any case, it's a yuurei.

Another word for poltergeists are noisy spirits(*3), as they are spirits which are able to make sounds.

The noises that poltergeists make are actually the yuurei of notes.

Since they're perceived by the spirit and not the ears, even beings without bodies can enjoy them.

At the same time, humans should be careful that its effect doesn't overwhelm them.

She is a very collected person, but she is recitent and glum.

The sounds she creates calm the spirit.

People who are overly influenced by her sounds will lose all motivation and become depressed.

She's said to live in a ruined Western mansion a bit farther from the lake than the Scarlet Devil Manor.

You won't see the sisters there even if you set foot inside.

However, it's said that you will hear the sounds of their practicing.

1: This is not meant to mean that its members are always absent.

2: They say this at the beginning of their live performances.

3: This may not be true. Poltergeists are said to be one form of magic used by young maidens.

"Sometimes I happen to come across a youkai party, but I'll end up joining in against my better judgment once I hear the Prismrivers' music playing." (Anonymous)

Humans should be able to join as well, as long as the youkai are still in the middle of their party.

"How can we call the Prismriver Ensemble to perform at an event?" (Fan club member no. 5)

You might have luck by going to the Ruined Western Mansion and making a request.

"The lead girl's pretty gloomy, so I don't really like her." (Anonymous)

She isn't human, so something horrible might happen to you if you say things like that too often.

She's very friendly to both humans and youkai, so you have nothing to fear from her.

It should be noted that the Prismrivers do not manage ticket sales for their live performances. Their clients do, so it is inadvisable complaining to the Prismrivers if you can't acquire on a ticket.

Their performances contain many notes that have a great effect on the spirit, so one should not attend unless one is in perfect mental condition.

Children should not be allowed to listen.

The notes of yuurei is a privilege for adults.